Random hardware fault and degradation protection apparatus for time-of-flight receiver

Abstract

A time-of-flight light detection system includes: a plurality of circuits arranged sequentially along a signal path that comprises a plurality of signal channels, the plurality of circuits including a first circuit and a second circuit arranged downstream from the first circuit; a reference signal source configured to generate a plurality of reference signals, where each of the plurality of signal channels at the first circuit receives at least one of the plurality of reference signals; and an evaluation circuit coupled to the plurality of signal channels to receive a processed reference signal from the signal path, the evaluation circuit further configured to compare the processed reference signal to a first expected result to generate a first comparison result.

What is claimed is: 
     
       1. A time-of-flight light detection system, comprising:
 a plurality of circuits arranged sequentially along a signal path that comprises a plurality of signal channels, the plurality of circuits comprising a first circuit and a second circuit arranged downstream along the signal path from the first circuit; 
 a reference signal source configured to generate a plurality of reference signals, wherein each of the plurality of signal channels at the first circuit receives at least one of the plurality of reference signals; and 
 an evaluation circuit comprising at least one processor, the evaluation circuit coupled to the plurality of signal channels to receive a processed reference signal from the signal path, the evaluation circuit further configured to compare the processed reference signal to a first expected result to generate a first comparison result, 
 wherein: 
 the first circuit is coupled to the plurality of signal channels and includes a first plurality of inputs corresponding to the plurality of signal channels and a first plurality of outputs corresponding to the plurality of signal channels, 
 the second circuit is coupled to the plurality of signal channels and includes a second plurality of inputs corresponding to the plurality of signal channels and a second plurality of outputs corresponding to the plurality of signal channels, and 
 each of the first plurality of outputs is coupled to a respective one of the second plurality of inputs by a respective one of the plurality of signal channels. 
 
     
     
       2. The time-of-flight light detection system of  claim 1 , wherein the reference signal source is a current source and the plurality of reference signals are current reference signals. 
     
     
       3. The time-of-flight light detection system of  claim 1 , wherein the evaluation circuit is configured to receive a plurality of processed reference signals from the signal path, each of the plurality of processed reference signals being derived from at least one of the plurality of reference signals, and the evaluation circuit is further configured to compare each of the plurality of processed reference signals to at least one of a plurality of expected results to generate a plurality of first comparison results. 
     
     
       4. The time-of-flight light detection system of  claim 3 , wherein the evaluation circuit is configured to receive the plurality of processed reference signals from at least two extraction points of the signal path. 
     
     
       5. The time-of-flight light detection system of  claim 4 , wherein the at least two extraction points include a first extraction point upstream from the second circuit and a second extraction point downstream from the second circuit. 
     
     
       6. The time-of-flight light detection system of  claim 3 , wherein the evaluation circuit is configured to:
 evaluate at least one characteristic of the plurality of signal channels based on the plurality of first comparison results, and determine whether the signal path is functioning normally based thereon. 
 
     
     
       7. The time-of-flight light detection system of  claim 1 , wherein the first circuit is a photodetector circuit and the second circuit is one of an amplifier circuit or an analog-to-digital converter circuit. 
     
     
       8. The time-of-flight light detection system of  claim 1 , wherein:
 the first circuit includes a photodetector array configured to generate electrical signals based on received light, 
 the reference signal source is configured to inject one of the plurality of reference signals into each of the plurality of signal channels at the first circuit such that each reference signal is combined with at least one of the electrical signals to generate combined signals that are processed by the signal path to generate processed combined signals, and 
 the evaluation circuit is configured to receive a processed combined signal from the signal path, the evaluation circuit further configured to compare the processed combined signal to a second expected result to generate a second comparison result. 
 
     
     
       9. The time-of-flight light detection system of  claim 8 , further comprising:
 a filter configured to receive the processed combined signals from the signal path and filter out the plurality of reference signals therefrom to restore the electrical signals; and 
 signal processing circuitry configured to generate object data based on the restored electrical signals. 
 
     
     
       10. The time-of-flight light detection system of  claim 8 , further comprising:
 signal processing circuitry configured to receive the processed combined signals from the signal path and generate first object data based on the processed combined signals; and 
 a filter configured to receive the first object data from the signal processing circuitry, detect virtual object data corresponding to the plurality of reference signals in the first object data, and remove the detected virtual object data from the first object data to generate second object data. 
 
     
     
       11. The time-of-flight light detection system of  claim 8 , wherein the evaluation circuit is configured to:
 evaluate at least one characteristic of the plurality of signal channels based on the second comparison result, and determine whether the signal path is functioning normally based thereon. 
 
     
     
       12. The time-of-flight light detection system of  claim 1 , further comprising:
 a memory device configured to store information corresponding to a plurality of different current pulse patterns; 
 a selection element configured to select one of the plurality of different current pulse patterns and control the reference signal source to generate at least one of the plurality of reference signals based on the selected one of the plurality of different current pulse patterns. 
 
     
     
       13. The time-of-flight light detection system of  claim 12 , further comprising:
 a system controller configured to modify a configuration of the signal path, and 
 wherein the selection element is configured to select one of the plurality of different current pulse patterns based on the configuration of the signal path. 
 
     
     
       14. The time-of-flight light detection system of  claim 13 , wherein the configuration of the signal path is a gain setting of at least one of the first circuit or the second circuit, wherein:
 for a first gain setting, the selection element is configured to select a first one of the plurality of different current pulse patterns, 
 for a second gain setting, the selection element is configured to select a second one of the plurality of different current pulse patterns, and 
 the first gain setting is larger than the second gain setting, and the first one of the plurality of different current pulse patterns has a smaller amplitude than an amplitude of the second one of the plurality of different current pulse patterns. 
 
     
     
       15. The time-of-flight light detection system of  claim 1 , wherein the first circuit comprises an analog multiplexer coupled to the plurality of signal channels and configured to receive the plurality of reference signals as inputs and route each of the plurality of reference signals to a different one of the plurality of signal channels. 
     
     
       16. The time-of-flight light detection system of  claim 15 , wherein the reference signal source and the analog multiplexer are controlled to implement a time shift of the plurality of reference signals such that adjacent channels of the plurality of signal channels receive corresponding reference signals of the plurality of reference signals at different times. 
     
     
       17. The time-of-flight light detection system of  claim 1 , wherein:
 a plurality of first time intervals are interleaved with a plurality of second time intervals, wherein the first circuit includes a photodetector array configured to generate electrical signals based on received light during the plurality of first time intervals, wherein the photodetector array is not providing signals to the signal path during the plurality of second time intervals, and 
 the reference signal source is configured to inject the plurality of reference signals into the plurality of signal channels at the first circuit during the plurality of second time intervals. 
 
     
     
       18. The time-of-flight light detection system of  claim 1 , further comprising:
 a system controller, 
 wherein the evaluation circuit is configured to detect a fault in the time-of-flight light detection system based on the first comparison result, and indicate the fault to the system controller, and 
 the system controller is configured to receive the fault and, in response thereto, perform at least one of: disable the time-of-flight light detection system, reduce a performance of the time-of-flight light detection system, or lower a priority of the time-of-flight light detection system relative to another object scanning sensor. 
 
     
     
       19. The time-of-flight light detection system of  claim 1 , wherein the reference signal source is configured to inject the plurality of reference signals between two light acquisition periods of the time-of-flight light detection system. 
     
     
       20. The time-of-flight light detection system of  claim 1 , wherein the reference signal source is configured to inject the plurality of reference signals during a light acquisition period of the time-of-flight light detection system. 
     
     
       21. A time-of-flight light detection receiver system, comprising:
 a plurality of circuits arranged sequentially along a signal path that comprises a plurality of signal channels, the plurality of circuits including a first circuit and a second circuit arranged downstream from the first circuit; 
 a reference signal source configured to generate a plurality of reference signals, each of the plurality of signal channels at the first circuit receives at least one of the plurality of reference signals; 
 the first circuit comprising a plurality of readout elements and a plurality of photodetector readout channels representative of a first portion of the plurality of signal channels and coupled to the plurality of readout elements, the plurality of readout elements configured to selectively route the plurality of reference signals to the plurality of photodetector readout channels; 
 the second circuit comprising a plurality of processing channels representative of a second portion of the plurality of signal channels, the plurality of processing channels including a plurality of processing elements configured to generate processed reference signals derived from the plurality of reference signals and output the processed reference signals from the second circuit; and 
 an evaluation circuit comprising at least one processor, the evaluation circuit coupled to the signal path to receive a processed reference signal of the processed reference signals, the evaluation circuit configured to compare the processed reference signal to a first expected result to generate a first comparison result. 
 
     
     
       22. A method of evaluating at least one characteristic of a plurality of signal channels in a time-of-flight light detection system that includes a plurality of circuits arranged sequentially along a time-of-flight light detection signal path that comprises the plurality of signal channels, the plurality of circuits including a first circuit and a second circuit arranged along the signal path downstream from the first circuit, the method comprising:
 generating a plurality of reference signals; 
 injecting at least one of the plurality of reference signals into each of the plurality of signal channels at the first circuit such that the plurality of reference signals are processed in the signal path; 
 generating a processed reference signal from a respective one of the plurality of reference signals by processing the respective one of the plurality of reference signals by at least one of the first circuit or the second circuit to generate the processed reference signal; 
 comparing the processed reference signal to an expected result to generate a comparison result; 
 evaluating the at least one characteristic of at least one of the plurality of signal channels based on the comparison result; and 
 determining whether either of the first circuit or the second circuit is defective based on the at least one evaluated characteristic of the at least one of the plurality of signal channels. 
 
     
     
       23. The time-of-flight light detection system of  claim 1 , wherein the processed reference signal is derived from a respective one of the plurality of reference signals by processing the respective one of the plurality of reference signals by at least one of the first circuit or the second circuit to generate the processed reference signal. 
     
     
       24. A time-of-flight light detection system, comprising:
 a plurality of circuits arranged sequentially along a signal path that comprises a plurality of signal channels, the plurality of circuits comprising a first circuit and a second circuit arranged downstream along the signal path from the first circuit; 
 a reference signal source configured to generate a plurality of reference signals, wherein each of the plurality of signal channels at the first circuit receives at least one of the plurality of reference signals; and 
 an evaluation circuit comprising at least one processor, the evaluation circuit coupled to the plurality of signal channels to receive a processed reference signal from the signal path, the evaluation circuit further configured to compare the processed reference signal to a first expected result to generate a first comparison result, 
 wherein the processed reference signal is derived from a respective one of the plurality of reference signals by processing the respective one of the plurality of reference signals by at least one of the first circuit or the second circuit to generate the processed reference signal.